1. Field of the Invention
The present invention relates to catalysts on inorganic carriers useful for preparing ethylidene diacetate and to methods for preparing and using those catalysts in a continuous process for manufacturing ethylidene diacetate represented by the following formula: ##STR1##
2. Background of the Invention
Various methods for producing ethylidene diacetate are known in the art. In all of these methods ethylidene diacetate has been prepared in batch reactor systems. Because known processes for preparing ethylidene diacetate employ a homogeneous catalytic reaction, there have been no known attempts to prepare this product by a continuous process. Conventional methods for preparing ethylidene diacetate have used homogeneous catalysts, e.g., transitional metals such as rhodium, ruthenium, palladium and platinum. Difficulties arose in separating these homogeneous catalysts from the reaction products.
There are few literature or patent references regarding methods for producing ethylidene diacetate. Several of these references disclose methods wherein methyl acetate, carbon monoxide and hydrogen are reacted in the presence of a homogeneous catalyst to produce ethylidene diacetate. While these methods which employ a homogeneous catalyst produce good selectivity and yield, all suffer from several significant disadvantages, including difficulties associated with separating and purifying the reaction products from the catalyst. Conventional homogeneous catalysts employed in these methods include complexes of group VIII transition metals, preferably rhodium, ruthenium, iridium, palladium and platinum. Japanese Patent No. 51-115409 and European Patent No. 0028474 disclose methods for producing ethylidene diacetate using a homogeneous rhodium catalyst. Japanese Patent No. 54-98713 and British Patent No. 1,112,555 disclose methods for producing ethylidene diacetate using homogeneous palladium catalysts. All of these methods suffer from difficulties in separating and purifying the reaction products from the homogeneous catalyst. These prior methods require the use of a distillation process to separate the homogeneous catalyst from the reaction products. For example, the '474 European patent, which discloses a method having a yield of 75.3% ethylidene diacetate based on dimethyl acetate starting material, requires a distillation step to separate the homogeneous catalyst from the reaction products.
The present invention solves the problems of the prior art by providing a novel catalyst system wherein the reaction products may be easily separated from a heterogeneous, supported catalyst. The catalyst and method of the present invention provide a simplified process for producing ethylirene diacetate and improve the productivity thereof while reducing the quantity of expensive, catalytic metal required.
By employing a catalyst supported on an inorganic carrier, the present invention solves the problems in the prior art caused by the difficulties in separating prior art homogeneous catalysts from the reaction products. The methods of the present invention simplify and improve the preparation and purification of ethylirene diacetate.